The first new sport added to the Winter Olympics since snowboarding in 1998, skimo is rooted in the 19th Century, before lifts to take skiers up mountains had been invented.
So, how does it all work?
The sprint events consist of both an ascent and descent, with athletes sprinting uphill with skins on their skis to provide traction, navigating a diamond-shaped obstacle on their way up to a stairway in the mountain.
They then remove the skis, placing them in their backpack, and continue climbing on foot, before a further uphill section on skis.
Once they reach the top of the course, they remove the skins, and ski downhill to the finish line.
The average duration of a race is about three minutes.
The speed and format of the competition meant fans were quickly invested in the absorbing contest and generated a lively atmosphere.
BBC commentator Matt Chilton said: “The ski mountaineering event has been so well-received.
“Televisually, it is superb. For the [in person] fans, they can see everything from the grand stand. They don’t miss a moment watching the action directly and on the big screen.”
Similar to the summer Olympic sport of triathlon, the transitions are key to a successful race.
That is ultimately what let Harrop down as she struggled in the second transition, getting the skins caught instead of ripping them off in one clean motion.
Harrop has English parents and could have represented Team GB but opted to compete for France, where she was born and bred.
She had topped both her heat and semi-final and looked on course for gold in the final but, after the second transition, was trailing behind Fatton and could not catch up on the downhill segment.
“It means a lot. When I look back to when I started the sport, it wasn’t even on the (Olympic) programme,” Harrop, who started out as an Alpine skier, said.
“I had an Olympic dream when I was an Alpine skier, and then when I stopped, it was just game over. So now to be here on this stage is mad.
“The atmosphere is good. The slope itself isn’t super technical, but today they made the downhill a little bit more technical than usual, so that was fun.”
A mixed relay event will take place on Saturday, where one man and woman from each nation completes two laps of the course each with a race typically lasting 30-40 minutes.
